Call processing to provide number portability

ABSTRACT

A method of routing a call including a called number in a communications network such as a Public Switched Telephone Network (PSTN), the method including determining if the called number is a network routing number indicating a specific switching node and line associated therewith in the communications network and routing the call within the communications network based on the called number when the called number is a network routing number. Additionally, the method includes identifying a network routing number based on the called number when the called number is not equal to the network routing number and routing the call within the communications network based on the identified network routing number.

Reference To Microfiche Appendix A microfiche appendix having 5microfiche and 413 frames is included herewith.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication network such as thepublic switched telephone network (PSTN) wherein call processing iscarried out to allow local number portability among numbers ported ormoved between an original switching node and another switching node andto allow subscribers within the communication network to maintain aparticular telephone or similar network access number regardless ofnumber relocation or porting within the communications network.

2. Description of the Related Art

In recent years there has been much discussion and effort to establishmethodologies, systems and solutions to the numerous issues pertainingto station number portability or local area number portability. Whilemany people agree that the central goal of local number portability isthe provision of a local (geographic) number to a network subscriberthat stays the same regardless of physical network, those same peoplehave often disagreed as to a particular solution to the local numberportability problem. Moreover, it is the fact that the public switchedtelephone network (PSTN) is a "legacy system" that exacerbates theissues pertaining to the provision of local number portability.

As such, many approaches have been proposed for providing local numberportability. Some of these approaches typically have been concerned withproviding "switch-wide" call routing solutions or other solutionswherein a network routing address is derived from or is numericallyrelated to an originally dialed number. For example, some solutions haveproposed elaborate plans that require transforming numbers from onedialing plan to another dialing plan, performing sophisticated mappingoperations in relation to the transformed numbers and then performingrouting that requires changes to existing switching and routinginfrastructures.

With switch-wide solutions to providing local area number portability,for example, call processing and routing are achieved by routing aported call to a particular end office system (e.g., a switchingcenters) for final call routing within that end office system.

One such switch-wide local number portability solution has been offeredby AT&T which is disclosed in U.S. Pat. No. 4,754,479 to Bicknell, etal. filed Sep. 17, 1986, issued Jun. 28, 1988 and entitled "STATIONNUMBER PORTABILITY." In particular, the '479 patent discloses a systemwhere a station number portability arrangement is provided that allows asubscriber who is ported from an original switch to a new switch toretain his or her originally assigned number regardless of any numberingplan constraints. Moreover, the system of the '479 patent requirescertain portability assumptions including that all switches that arecapable of porting must be within a single portability cluster, thatcalls are to be routed to a particular destination switch and that thedestination switch is capable of performing certain database operationsto ultimately route a call to a particular line.

A system of the type described in the '479 patent has certain drawbacksincluding a course granularity in terms of ultimate line particularity(i.e., only switch-wide porting is possible as opposed to line-specificporting) and a requirement that each destination switch must be capableof performing certain database operations to perform a subsequentline-specific routing.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to providea local number portability solution that addresses the drawbacksassociated with prior art call routing systems to provide numberportability.

It is another object of the present invention to provide a local numberportability solution that routes ported or relocated or moved numberstransparently of the telephone call routing scheme that is used toactually route a call within a particular switch at a particular endoffice.

It is a further object of the present invention to provide a localnumber portability solution that allows customers to retain anoriginally assigned number regardless of a change in service providers.

It is an additional object of the present invention to provide a localarea number portability solution that allows network routing of callsincluding ported calls by without requiring a change in establishednumbering plans.

It is also an object of the present invention to provide a local areanumber portability solution that allows network routing of callsincluding ported calls without requiring a change in establishednumbering plans and which operates with current switching systems.

It is still a further object of the present invention to provide a localarea number portability solution that allows network routing of callsincluding ported calls making certain assumptions about switching nodesand the routes on which calls are received at such switching nodes.

It is yet a further object of the present invention to provide a localarea number portability solution where a customer number address ismapped to a network node address and where the customer number addressand the network node address have the same format.

It is yet another object of the present invention to provide a localarea number portability solution that allows network routing of callsincluding ported calls to a particular switching node and a particularline thereof in a communications network.

It is still a further object of the present invention to provide a localarea number portability solution that may be used to provide linespecific portable number routing.

It is a further object of the present invention to provide a local areanumber portability solution that may be used to provide switch-wideportable number routing.

These and other objects and advantages are achieved by the presentinvention by providing a method of routing a call based upon a callconnection request including a called number in a communicationsnetwork. The method includes a step of determining if the called numberis equal to a network routing number and routing said call within thecommunications network based on the called number when the called numberis equal to the network routing number. The method also includes thestep of identifying the network routing number based upon the callednumber when the called number is not equal to the network routing numberand routing the call within the communications network based on theidentified network routing number.

The objects of the present invention are also achieved by providing Amethod of routing calls within a communications network interconnectinga plurality of switching nodes wherein at least some switching nodes ofsaid plurality of switching nodes are capable of routing and terminatingported numbers. The method includes a step of generating a callconnection request including a called number. Additionally, the methodincludes a step of determining if the called number matches a triggerindicating that the called number may be a ported number and routing thecall based on the called number when the called number does not matchthe trigger. Also, the method includes the step of determining if thecalled number has been translated into a network routing number when ithas been determined that the called number matches the trigger.Additionally, the method includes a step of translating the callednumber into a translated network routing number when it has beendetermined that the called number had not earlier been translated androuting the call based on the translated network routing number.

Finally, the objects of the present invention are further achieved byproviding a method of routing a call including a called number in acommunications network. The method includes the steps of determining ifthe call is from a first domain of the communications network andtranslating the called number into a network routing number when thecall is from the first domain.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described objects and advantages of the present invention aredescribed with reference to the appended drawing figures of which:

FIG. 1 is a call flow diagram of a call to a ported number in acommunications network wherein local number portability is supportedaccording to the present invention.

FIG. 2 is another call flow diagram of a call to a ported number in acommunications network wherein local number portability is supportedaccording to the present invention.

FIG. 3 is another call flow diagram of a call to a ported number in acommunications network wherein local number portability is supportedaccording to the present invention.

FIG. 4 is a diagram that illustrates a database construct to bring aboutnumber translation to derive a NANP format routing number for routingported numbers according to the present invention.

FIG. 5 is a high-level flow chart generally illustrating the operationsof the present invention to bring about local number portability.

FIG. 6 is a flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 7 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 8 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 9 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 10 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 11 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 12 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 13 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 14 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 15 is another flow chart that illustrates in detail the operationsgenerally depicted in FIG. 5.

FIG. 16 is a flow chart that illustrates the routines carried out by thepresent invention to provide line-specific portable number routing.

FIG. 17 is a diagram that illustrates the origination and routing ofcalls within a communications network including calls from new and olddomain switching networks.

FIG. 18 is a diagram that illustrates a database architecture used tobring about domain partitioning according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The presently preferred embodiments of the present invention are nowdescribed with reference to the appended drawing figures which werebriefly described above. In the appended drawing figures and in thefollowing paragraphs, like parts and items are referred to with likereference numerals and labels.

In reviewing the attached drawing figures and the discussion of thepresent invention as provided herein, it is important to keep in mindthe following points. First, the present invention is directed to thetopic of what is actually called "Geographic Number Portability" asdistinguished from "station portability" as that term may be used in theart. That is, the present invention is directed to providing aportability solution for providing subscriber numbers wherein (1) suchnumbers are hierarchically routed, (2) numbers have a geographicalsignificance, (3) such numbers are typically not of the 800, 700, 500 or900 type, for example, and (3) such numbers contain a North AmericanNumbering Plan (NANP) format wherein a translated NPA-NXX is uniquelyassigned to a particular end office (EO) of the public switchedtelephone network (PSTN) (i.e., the communications network to which thepresent invention is directed).

Geographic number portability also has been termed "local numberportability" and "local area number portability." As such, these termsfor portability are treated herein synonymously. Second, the presentinvention provides number portability or local area number portabilityby de-coupling a user-dialable phone number (e.g., voice or data calls)from a network routing number that is used within the public switchtelephone network (PSTN) to route and terminate a call. Today, the useof user-dialable numbers and network routing numbers are implicitthroughout the PSTN and all related support systems. As such, since theuser-dialable number and the network routing number are implicitly thesame number which is directly tied to their serving facilities (i.e. theowning service provider), such numbers inherently are not portable.

As such, it can be said that portability fundamentally requiresde-coupling the two identified uses of a number so that the samecustomer number (or Customer Name Address--CNA) may be associated withdifferent service providers and hence different serving facilities(addressed by a Network Node Address--NNA) at different points in time.That is, different customer numbers can be assigned to the same stationat different times. This decoupling enables the customer to keep hisexisting number and change service providers through a change in thedatabase record that maintains the mapping between the customer's number(CNA) and his chosen serving facilities (NNA). Local area numberportability therefore calls for the recognition that each of the twofunctions for a number (customer dialable access and network routing)creates two independent numbering plans, one for each function (i.e., aCNA numbering plan and a separate NNA numbering plan).

Third, a core distinguishing attribute of the present invention'ssolution to offering number portability is the proposed format for thenetwork routing number of the NNA. It is well known that CNA's mustcontinue to be the familiar 7/10 digit NANP numbers to prevent requiringcustomers or subscribers to change their numbers even once to obtain aportable number. The present invention supports number portabilitywithout requiring a change in customer's existing numbers. Moreover,NNAs within the present invention also use 10 digit routing sequences sothat existing PSTN routing systems can be used for call routing, switchprovisioning, switch translations and switch-based vertical services(e.g., CLASS). Furthermore, the present invention implements the NNAnumbering plan as a separate, identical, number plan from the CNA plan.This incremental separation of dialing and routing functions of the10-digit extends significantly extends the life cycle of the existing10-digit NANP format for both uses and especially for dialable numbers.The long-term strategy of functional separation of the numbering space,as proposed by the present invention, isolates the 10-digit CNA universeof customer numbers from impacts resulting from the inclusion of newtechnologies such as a PCS and ATM into the PSTN.

Finally, the present invention is also theoretically based on thepremise that routing numbers or NNAs identify both the terminating endoffice (EO) as well as the line/trunk termination, exactly as 10-digitnumbers in the NANP do today. The use of 10-digit NNAs enables thedeployment of service provider local number portability (LNP) withexisting network infrastructure. Call translation state trackingmechanisms defined within the present invention enable NNA to beseparated from CNAs thereby enabling number portability to be deployedwithout wasting precious NANP resources.

With the foregoing comments in mind, reference is now made to thedrawing figures. Referring now to FIG. 1, therein depicted is anexemplary call flow diagram of a call routing scenario in acommunications network system incorporating line-specific routing toachieve local area number portability according to the presentinvention. It is important to note that while line specific routing isused for purposes of illustration, it is to be understood that theultimate routing paradigm that is incorporated into the terminating endoffice that ultimately routes the call to a ported number is independentof the present invention's ability to translate CNAs to NNAs. It is theprovision of all relevant information including switching node and lineidentification information through use of a NANP like number in the formof the NNA that allows any routing paradigm to operate at an end officewithout requiring a change in infrastructure within that end office tobe used. For example, the provision of a NANP like NNA routing number,as provided by the present invention, allows an end office, such as anoffice that may or may not be capable of porting or one that is capableof porting on a switch wide basis only or one that provides cellularrouting, to properly route calls to subscribers affiliated with such anend office to be used. As such, it should go without saying that theembodiments discussed herein are meant to be applicable to anycommunications network having any sort of routing system that iscompatible with the PSTN.

Additionally, FIGS. 1, 2 and 3, illustrate certain structures andcorresponding operations that are carried out by particular computerhardware and software devices. For example, the item identified as LEC-1refers to a local exchange carrier such as a Regional Bell OperatingCompany or RBOC. A typical LEC will have the necessary computer hardwareand software to route and, possibly, translate calls. In particular,LEC-1 is shown to include a Service Switching Point or SSP 12 that isSS7 communications network compatible. A typical SSP will include aswitching complex such as an AT&T 5E or DMS 100 and switching softwarecommonly referred to as a "switching generic." The computer equipmentassociated with the switch of the SSP along with the switching genericare capable of detecting when database queries need to occur for aparticular call to be routed through the switch (i.e., capable ofdetecting if a portability trigger condition is presented at the SSP bya call as discussed below in regard to FIG. 5, for example).

Additionally, a typical SSP will be able to suspend calls so thatappropriate database queries for portability purposes can be sent to aservice control point or SCP 14 (designated in the drawing as an LNPdatabase for portability) that includes a database system and await fora response message therefrom. The SSP is also capable of processingcalls based on the response message received from SCP 14.

The typical SCP 14 includes computer hardware and software for carryingout service control and database operations for a call. In particular,such computer hardware includes a central processing unit or CPU, arandom access memory unit (RAM), disc storage and input/out (I/D)components that communicate via well known SS7 links.

Additionally, the computer software typically maintained at SCP 14includes a database management system (DBMS) which may be RAM residentand which supports RAM resident operations for high speed databasequerying. Also, certain application processes for SS7 communications runon the SCP for performing such processes as number translation asdefined by the present invention and for forming response messages andthe like.

The hardware that is found at SCP 14 may include a STRATUS CONTINUUM1245 computer and support peripherals. The software will typicallyinclude an operating system (OS) such as the FTX OS (i.e., a version ofUNIX) and a DBMS such as ERDB as distributed by ATA, INC.

Each SSP in FIG. 1, as well as in FIGS. 2 and 3, will be connected orcoupled to an SCP via the SS7 network via SS7 A-links which are wellknown.

The aforementioned structures operate as illustrated in FIG. 1, so thata call via a called number is initiated at a station 10 from anoriginating LEC. While station 10 is shown as being a telephone, itshould be understood that station 10 may be any form of telephony devicethat is capable of initiating or forwarding a call within acommunications network such as the PSTN. Moreover, it should beunderstood that station 10 may be capable of initiating or forwardingany type of call including data and fax calls over either plain oldtelephone service or POTS or over digital networks, such as over ISDN.Additionally, while it may be said that a particular station, such asstation 10, has a fixed or specific line address within thecommunications network, it is the access number associated with anyparticular station, such as station 10, to which the present inventionis directed.

Station 10 is associated with SSP 12 having an NNA NPA-NXX office codeof "206-971." It will be understood that the SSP associated with the206-971 office code is maintained by a local exchange carrier that isidentified as "LEC-1." It should also be understood that the dialednumber will be converted into an appropriately formatted (i.e., NANP10-digit format) Customer Name Address (CNA) number in a conventionalmanner. The SSP 12 associated with LEC-1 is capable of routing andterminating ported numbers; that is, LEC-1 has a switching system thatsupports portability.

At number (2) in the figure, a database access "dip" is performed to mapor translate the CNA to a Network Node Address (NNA) number. The NNAalso has a standard NANP 10-digit format. The table associated with thedatabase lookups and queries to bring about mapping is illustrated inFIG. 4 as discussed below.

As such, in LEC-1 the CNA (i.e., the portable called party number(CdPN)) has been mapped to an appropriate NNA (i.e., 206-623-9867) whichthe communications network (e.g., the PSTN) may rely on to properlyroute the call to the end office switching node 18 in LEC-3 asillustrated by the line marked as (3). LEC-3 ultimately may be orinclude a cellular network for example. Moreover, it should beappreciated that the NNA contains both an end office code (i.e., aswitching node address--206-623) and a line number associated therewith(i.e., line number 9867). Accordingly, the NNA is a routing numberwithin the communications network that indicates a specific switchingnode 18 and a specified line or station 20 thereof to which the callshould be properly routed. As mentioned above, the terminating accessprovider or end office switching node 18 (e.g., LEC-3) ultimately maynot use all information contained with the NNA to route the call tosubscriber station 20.

It should also be noticed that in LEC-1, the CNA (i.e., the formatteddialed number or CdPN in the figure) was examined and determined to be apossibly ported or relocated number. That is, the call parametersassociated with the CdPN contained what is called a "trigger" indicatingthat a translation or "dip" should be done or should have been done totranslate the CNA into an appropriate NNA. While triggering is animportant part of the operations of the present invention, triggeringtechniques are well known and have received a significant amount oftreatment by the industry. As such, many solutions to triggering havebeen proposed. For example, one such triggering approach has beenproposed by Ericsson in U.S. Pat. No. 5,377,186 to Wegner, et al.entitled "SYSTEM FOR PROVIDING ENHANCED SUBSCRIBER SERVICES USING ISUPCALL-SETUP PROTOCOL" which approach is incorporated herein by reference.

Additionally, it should be noted that FIG. 1 illustrates a situationwhere a dip (i.e., a mapping from a CNA to an NNA) is performed in LEC-1which is the next-to-last to the ultimate network (i.e., LEC-3) andswitch 18 that will receive and terminate the ported call where the callis completed to station 20 at number (4) for station 20. Thisnext-to-last approach is considered by the inventors to be a desiredtriggering location strategy which has been termed the "N-1 Policy."While it is desired to realize dipping or triggering at the N-1 networkalong the call path, it should be understood that there is no positiverequirement that such should occur.

Also, FIG. 1 illustrates a communications network wherein three LECs are"new domain." That is, LEC-1, LEC-2 and LEC-3 are all capable of routinglocal number portable (LNP)calls and terminating ported numbers.Accordingly, for purposes of clarity, when the terms "new domain" and"old domain" are used throughout this document, the same are meant torefer to a group (i.e., new domain group) of switching nodes or networks(i.e., LECs and/or particular SSPs) that are capable of routing LNPcalls and terminating ported or movable numbers and a group (i.e., olddomain group) that is not so capable, respectively. The presentinvention is capable of routing calls regardless of the domain fromwhich a call originates and regardless of the domain to which a call isto terminate because of the format of the present invention's NNA.

It should also be understood that while the present invention may beused to actually route calls in a communications network based on an NNAthat indicates a specific switching node and a line thereof, the presentinvention is not so limited. That is, while the translation of a CNA toNNA includes determining a specific switching node and line thereof forterminating a call, the particular routing approach may use any part ofthe information contained within an NNA to route a call. It is thepresent invention's ability to provide a fine granularity in terms ofits translation from CNA to NNA that supports a variety of physicaltranslation schemes at a terminating end office. For example, thepresent invention now makes it possible to map or translate callednumbers or CNAs into network routing addresses or NNAs that supportphysical call translations based on a line specific number portabilitytranslation paradigm, a switch-wide number portability translationparadigm or even a cellular network translation paradigm. Moreover, itshould be understood that as new translation paradigms are developed andimplemented, the present invention will support the same. It should benoted that routing is to be distinguished from translation and thattranslation should be understood to have no effect on the physicalrouting of calls within a communications network such as the PSTN. Thatis, the present invention maintains the independence of call routingfrom the interpretation and indication of the called party number (CdPN)at a terminating end office.

Finally, it should be understood from inspection of FIG. 1, and fromFIGS. 2-3 as discussed below, that originally (e.g., prior to the adventof number portability) a CNA is equal to an NNA. Only after a portingfrom an original end office or LEC to another end office or LEC willthere be a logical separation or porting of CNA to a physical routingnumber or NNA. For example, in FIG. 1, the subscriber having the number812-1234 has ported or moved from LEC-2 to LEC-3. Moreover, thesubscriber having the number 623-9867 ported or changed serviceproviders by using LEC-3. In other words, FIG. 1 shows a situation wheretwo subscribers cross-ported (i.e., relocated their respective NNAnumbers) while maintaining their originally provided telephone numbers.As such, prior to any subscriber porting, the number 206-816-1234originally indicated both a CNA and an NNA. Only after porting would atranslation as provided by the present invention reveal that the CNA206-812-1234 mapped to the NNA of 206-623-9687. As such, it should beappreciated that number portability can occur as a result of asubscriber electing to change their service provider, their geographiclocation or their type of service (e.g., plain or telephone service orPOTS to a digital network such as ISDN).

Referring now to FIG. 2, therein depicted is a communications networkthat includes both new (SSP) and old domain (EO) switching systems. Inparticular, LEC-1 is an old domain switching node or end office 22 thathas the NPA-NXX office code of 206-971. The dotted line in FIG. 2illustrates a logical domain partition between an old domain and a newdomain. As such, at number (1) when the call is initiated at a stationassociated with LEC-1 by dialing the number 812-1234, end office 206-971or SSP routes the call at number (2) to an end office 23 with theNPA-NXX office code of 206-812 in a conventional manner. That is, LEC-1does not have the ability to dip the call as it is in the old domainand, as such, LEC-1 routes the call to 206-812 by interpreting the CNAas an NNA as is done for non-ported numbers. This type of conventionalrouting (or routing based on the CdPN) is also a default condition forthe present invention. It should be noted that it is the switch at theend office of LEC-1 that is not an LNP participating switch that makesLEC-1 part of the old domain.

In LEC-2 the SSP 23 including LNP 14 containing end office code 206-812receives the call where the CNA has the NANP format and is equal to206-812-1234. At LEC-2, the non-originating LEC, the CNA and the NPA-NXXof the CNA will be recognized as a ported NXX and a dip will beperformed at number (3). As discussed with regard to FIG. 1, a dip isperformed to map or translate the CNA to an appropriate NNA. Thereafterthe NNA will be used to route the call to a particular switching node orcomplex and a particular line thereof. In this case, the dip performedby SSP 23 translates the CNA (206-812-1234) into the NNA of206-623-9867. Accordingly, the communications network depicted in FIG. 2will route the call to the SSP 18 in the LEC that maintains end officecode 206-623. Additionally, the SSP 18 of LEC-3 may examine the NNA todetermine the actual line number 9687 associated with LEC-3 to route thecall to subscriber station 20. As such, SSP 18 of LEC-3 need not performa database query to determine an appropriate line routing number aswould be done in a switch-wide routing system. Instead, upon receipt ofthe call in LEC-3, SSP 18 of the LEC-3 will already know how to routethe call based on the translation of the CNA to the NNA that occurred byway of the dip by the SSP 23 at LEC-2. However, as noted above, LEC-3may utilize any particular routing paradigm to route the call and, assuch, LEC-3 may utilize the NNA in any fashion. The present inventionhas achieved its routing objectives by properly mapping the CNA to anNNA. The actual routing paradigm that LEC-3 utilizes is not important.

As in FIG. 1, the communications network of FIG. 2, performed the dip atthe N-1 network (i.e., SSP 23 of LEC-2) along the call path to route thecall to the appropriate switching complex (i.e., SSP 18 of LEC-3 ).Again, while N-1 dipping is preferred the present invention is not to beso limited and it is to be understood that N-1 dipping is a desiredpolicy for placement of the translation process.

Finally, at SSP 23 of LEC-3, the call is completed at number (5) tosubscriber station 20 wherein the CdPN was translated from 206-812-1234to the physical number 206-623-9867 and that station 20.

Referring now to FIG. 3, therein depicted is another exemplary call flowdiagram of a call routing sequence wherein a portable number is mappedand routed to a particular network address and location. In particular,a long distance portable number call is initiated by dialing at number(1) at station 36 in LEC-1. Immediately, SSP 38 of LEC-1 recognizes thatthe dialed number contains a CNA that is a toll-call or long distancerequest. Accordingly, SSP 38 of LEC-1 routes the call the subscriber'spre-selected inter-exchange carrier (IC or IXC) in a conventionalmanner. The IC or IXC is often referred to as a preselectedinter-exchange carrier or PIC. It does not matter whether LEC-1 is a newor old domain type as the initial routing in the present call flowdiagram is to transmit the call to the IC in a conventional manner.

In FIG. 3, the IC (SSPs 40 and 42) is a new domain entity and is capableof dipping calls. It is noted that most, if not all, IXCs will be newdomain participants in the PSTN. Accordingly, the IXC recognizes thatthe called party number or CNA (206-812-1234) is a ported numbertherefore requiring translation via a database dip. As such, the dip isperformed at the IXC at number (3) by SSP 40 to map the CNA to theappropriate 10-digit NNA 206-623-9867. Thus, the call will next berouted at number (4) by SSP 42 in a possibly conventional manner via SSP44 at LEC-3 based on the NNA to the line numbered 9687 at the end officehaving the NPA-NXX office code of 206-623 where the call is completed orterminated at number (5) by a connection to station 46.

It should be noted that while the N-1 policy for dip placement at thenext-to-last switching network is preferred. The dip in FIG. 3 wascarried out at the first SSP of the IXC which ultimately caused the callto be routed through another SSP which actually routes the call. WithIXCs, it very often will be the case that the N-1 policy cannot beachieved since such IXCs are often only coupled to a particular LEC orswitch carrier which must route calls appropriately for such IXCs. Inother words, as IXCs are dependent on particular LECs for routing and asIXCs cannot be connected to every LEC, there may often be the case thatthe N-1 policy cannot be enforced. Accordingly, it is the presentinvention's ability to determine if a call has already been dipped whichis one of the things discussed in detail below that allows properrouting to occur regardless of whether the N-1 policy may be enforced.

At this point in the discussion of the present invention, it should beappreciated that it is the format of the NNA that allows any particularend office switching system of the communications network, includinglegacy systems, to route calls without requiring a change in numberingplans or numbering formats.

Referring now to FIG. 4, therein depicted is a database record formatused by the present invention to map CNAs to NNAs during a dip process(i.e., during a process to translate a customer number address into anetwork node address that identifies a particular switching node and aparticular line thereof to which a call should be routed). Databasestructure 16 defines one entry of a table indexed on CNA which containsrecords that define a mapping from CNA to NNA. Additionally, otherfields such as Vacant (VAC.) and Type are maintained in the table andare described in detail below in regard to FIGS. 6-16. Also, databasestructure 16 includes a field identified as SERVICE PROVIDER which maybe used to indicate the name or identifier of the provider for theported or movable number which may also be used for routing purposes. Itis important to note that the CNA and the NNA within the presentinvention bear the same format--that is, the CNAs and the NNAs of thepresent invention are formatted in a manner consistent with the NANP. Assuch, this distinguishing feature of the present invention allows numberportability to be realized across legacy and state-of-the-art telephonyswitching platforms that may be found in the PSTN. Moreover, bydecoupling the customer number and an associated network routing numberportability is achieved. Additionally, by maintaining a paradigm thatthe NNAs within the portability approach look like NANP numbers, agraceful transition to number portability can be achieved by the presentinvention.

Referring now to FIGS. 5-17, therein depicted are flow charts thatillustrate the operations of the present invention to provide local areanumber portability. The flow charts of FIGS. 5-17 and the discussionsherein are meant to summarize the actual routines that have beenimplemented in computer software to control appropriate computerhardware and switching technologies to bring about local numberportability and which have been attached to this document in the form ofan appendix that was particularly identified above. For a detailedunderstanding of the implementation details of the various routinesillustrated in the flow charts and/or mentioned herein, the reader isdirected to the above-mentioned appendix.

Referring now to FIG. 5, therein depicted is a high-level flow chartgenerally illustrating the operations of the present invention carriedout at a switching node such as a LEC or IC to bring about local numberportability in a communications network such as the PSTN wherein a callis initiated either from an originating subscriber or from a switch thatis referred to as being upstream along the call path.

A call is initiated at step 100. The initiated call may include a portedor movable number such as 812-1234 which will be converted to a NANPnumber format containing a 10-digit number sequence in a conventionalmanner (i.e., the end office code of the NPA NXX office code will beadded to the initiated call or dialed number). Thereafter, adetermination is made at step 110 as to whether the dialed number is atoll call in a conventional manner (e.g., does the call contain a "1plus" sequence?). If the call is a toll call such as a long distancecall, processing proceeds to step 120 wherein the call including the CNAare routed to an IC or IXC for appropriate routing and call processing.It should be appreciated that as the flow charts of FIGS. 5-17 are meantto depict processing at any point along a call path, the IXC wouldcertainly cause an instance of the processing depicted within FIGS. 5-17to occur. Accordingly, it should be understood that the IC or IXC may ormay not dip a call to translate a CNA to a NNA for appropriate callrouting.

If the call is not a toll call, processing proceeds to a determinationat step 130 as to whether local number portability (LNP) routines shouldbe performed in relation to the called party number (CdPN) or CNA. Inother words, step 130 determines by examining the CNA whether the CNAcontains a trigger indicating the presence of a possibly ported number.Another way to look at the processing of step 130 is to say that at thisstep, a determination is made as to whether the CdPN is a CNA or NNA.

If LNP operations are not necessary (e.g., in the case that the calledparty number immediately maps to a line that is present on the switchingnode that handled the call initiation such as directory assistance, forexample), then call processing continues at step 140 wherein the call isconventionally routed based on the CdPN which is the CNA.

If LNP operations are necessary (i.e., a trigger is in effect and theCdPN or CNA is to be translated to an NNA because the called party hasported or moved to another LEC or service system), processing proceedsto step 150 where LNP routines are performed to translate the CNA to anNNA (i.e., the call is dipped) and the call is routed appropriately. Asnoted above, the mapping from CNA to NNA is one in which the CNA ismapped to a particular switching node and a particular line associatedwith that switching node to provide line specific routing, if possible.

Thereafter, processing ends and a dialed number (i.e. CdPN) willappropriately routed in the communications network of the PSTN via aCdPN routing algorithm.

Referring now to FIGS. 6-17, therein provided are flow charts toillustrate in detail the operations generally depicted in FIG. 5. Inparticular, a call is initiated at step 200 as described above. It isnot important whether the call is a voice call or a data call. Only thedialed number as it relates to a CNA is important.

At step 210 a determination is made as to whether the dialed number is atoll call. If the dialed number is a toll call, the call is routed to aPIC (pre-set or preselected inter-exchange carrier) for toll callprocessing and routing. As noted above, the PIC may also be set up todip calls to translate CNAs to NNAs as provided herein.

If the dialed number is not a toll call, processing proceeds to step 230where a determination is made as to whether the dialed number (as in theform of a CNA) contains a trigger as suggested above. The routines todetermine if a trigger is in effect are discussed below with regard toFIGS. 9 and 10. If no trigger is in effect (i.e., the call cannot be aported number), processing proceeds to step 240 where the call is routedon the called party number (i.e. CdPN) in a conventional manner.

If a trigger is in effect (i.e., the dialed number may be a portednumber), processing proceeds to step 250 wherein a database query islaunched (i.e., a dip is performed) to translate the CNA to NNA or todetermine that a dip had already occurred at a previous place in thecall path and that the number in the CdPN field of the call signallingprotocol is already an NNA. The details of performing a dip arediscussed below with regard to FIGS. 11, 12 and 13. It is important tonote, however, that it is crucial to be able to determine if a call hasbeen previously dipped as redundant dipping and dipping on an NNA canlead to problems including wasteful allocation of system resources suchas database operations and erroneous mapping leading to erroneous callrouting. The present invention provides solutions to such problems whichare discussed below with regard to FIGS. 14-15 and which provide foraccurate routing regardless of redundant dipping.

In FIG. 7, processing proceeds at the SCP (i.e., in the database) and tostep 260 where, as suggested above, a determination is made as towhether the call and the CNA as formed by the providing LEC has alreadybeen translated. If the call has already been translated processingproceeds to step 270 where a RETURN code is returned in thecommunications network as in the case of the AIN 0.1 protocol and thecall is routed on the CdPN which has been replaced with an appropriateNNA that indicates a particular switching node and line thereof forterminating the call.

If the call is not translated, processing proceeds to step 280 where ascan of appropriate databases maintained at current switching node for aCNA table record is performed. The databases maintained at the currentswitching node are duplicates of databases that a party such as aregional third party maintains to provide local number portability. Itis not important to the present invention as to who or what entityactually maintains the original mapping tables. All that is important isthat the current switching node that is capable of performing the diphas such a mapping table available for processing.

At step 290 a determination is made as to whether a CNA table record wasfound as a result of database operations. If a CNA table record does notexist, processing proceeds to step 300 where a RETURN code is returnedas in the case of the AIN 0.1 protocol and the CNA is assumed to benon-ported and the call is routed on the CdPN (i.e., the CNA is the NNA)in this case.

If the CNA table record exists, processing proceeds to step 310 in FIG.8. At step 310, a determination is made as to whether the CNA tablerecord indicates that the CNA is flagged as Vacant (i.e., no destinationaddress is associated with the dialed number). If the CNA is flaggedVacant, processing proceeds to step 320 where a RETURN code is sent backfrom the database service processing the dip and the call is providedwith a Vacant Call Treatment such as a recording that indicates that"YOUR CALL COULD NOT BE COMPLETED AS DIALED PLEASE TRY YOUR CALL AGAIN."

If the CNA is not flagged as Vacant, processing proceeds to step 340where call routing is achieved as further illustrated and discussed inregard to FIG. 16.

Turning now to FIGS. 9 and 10, the flow charts provided therein areexpansion flow charts for step 230 as shown FIG. 6. In particular, FIGS.9 and 10 illustrate the routines that may be carried out to determinewhether a trigger is in effect. That is, the steps carried out in theflow charts of FIGS. 9 and 10 determine if the call parametersassociated with the call and the called party number (CdPN) as formedinto a NANP like CNA contain an indication that the CdPN is a portednumber. The steps may be carried out in any sequence.

In particular, at step 370 of FIG. 9, a determination is made at the SSPlevel as to whether the CNA contains a public office dialing plan (PODP)trigger according to the AIN 0.1 call processing protocol, incorporatedby reference herein. The acronym AIN stands for Advanced IntelligentNetwork. If such a trigger is in effect, the database query processordetermining if a trigger is in effect (i.e., a module that communicateswith the particular switching node that is now handling the call alongthe call path) sends the switching node now handling the call along thecall path an AIN 0.1 INFOANALYZE instruction message and the call isrouted accordingly. Such call routing will be apparent to those skilledin the art.

If a public office dialing plan (PODP) trigger is not in effect,processing proceeds to step 390 where a determination is made as towhether an IN/800 style trigger is in effect in relation to the CNA. Ifan IN/800 trigger is in effect, processing proceeds to step 400 where an800-number style query is handled by an appropriate processing unit thatis well known in the art and the call is routed accordingly.

If an IN/800 trigger as defined in Bell Core Document # TR-NWT-000533,incorporated by reference herein, is not in effect, processing proceedsto step 410 where a determination is made as to whether an AIN DNTtrigger is in effect in relation to the CNA. If such a trigger is ineffect, an AIN 0.0 query is launched in a conventional manner and thecall is routed accordingly.

If an AIN 0.0 trigger as defined in Bell Core Document # TR-NWT-001284,incorporated by reference herein, trigger is not in effect in relationto the CNA or dialed number as formatted into a NANP 10-digit number,processing proceeds to step 430 in FIG. 10. At step 430, a determinationis made as to whether a translation of the CNA to an NNA should be donebased on an ISUP trigger assist approach. If ISUP trigger assistprocessing is to occur based on the CNA, processing proceeds to step 440where the call is routed to an SCP or SSP where the CNA can beappropriately translated (i.e., where the CNA can be mapped to the NNA).

If ISUP trigger assist processing is not to occur, processing proceedsto step 450 where no trigger has been determined to be effect inrelation to the CNA and the call is routed on the CdPN and the CNA canbe thought of as the NNA. In other words, the CNA will not besubsequently mapped as number portability is not desired and the call isrouted on the 10-digit CNA in a conventional manner.

It should be understood that triggering is not limited to the approachesillustrated in FIGS. 9 and 10. The trigger determinations fordetermining whether to carry out number portability operations withregard to a particular CNA at an arbitrary point in a call path mayinvolve any type of trigger which network operators believe optimizesthe determination process. In particular, it is presently envisionedthat new triggers will be developed and deployed at switching nodes thatare especially optimized for triggering to number portability processes.While triggering is a critical element of any number portabilityapproach and solution, it is well known that triggering techniques arereally switch vendor issues which will be carefully developed as numberportability becomes implemented. For a further discussion of triggeringtechniques, the reader's attention is directed to U.S. Pat. No.5,377,186, to Wegner, et al. entitled "SYSTEM FOR PROVIDING ENHANCEDSUBSCRIBER SERVICES USING ISUP CALL-SETUP PROTOCOL" which isincorporated herein by reference.

Referring now to FIGS. 11-13, therein provided are flow charts thatexpand operational steps 250 and 260 as originally shown in FIGS. 6 and7, respectively. In particular, FIGS. 11-13 illustrate the operations ofthe present invention to carry out a database operation that hasheretofore been referred to as a "dip" and to determine if such a diphad earlier been performed at another point in the call path. A dip isperformed to basically do two things: (1) to determine if a dip has beenpreviously done at another point along the call path for the particularcall that is being routed, and (2) if a dip had not been previouslyperformed, to map or translate the CNA to an NNA which may be used toroute the call to a particular switching node and a particular linethereof.

Accordingly, at step 460 in FIG. 11 a determination is made as towhether the call signalling parameters contain a MAGIC ANI/II value. Theterm MAGIC refers to a value that has been designated by involvednetworks to indicate portability operations. The MAGIC value may or maynot be standardized. The present invention's use of the ANI/II parameteris consistent with the use of the same within the PSTN. If such a valueis include in the call signalling parameters, the CNA is perceived to bethe NNA and, accordingly, a CONTINUE return code is returned from thedatabase query processor performing the dip to the relevant switchingnode and the call is routed on the CdPN.

If the call signalling parameters do not contain a MAGIC ANI/II value,processing proceeds to step 480 wherein a determination is made as towhether the CNA contains an ISUP forward dip indicators, such as FCI orNature of Number CdPN. If so, a CONTINUE return code is returned fromthe database query processor performing the dip to the relevantswitching node and the call is routed on the CdPN.

If the CNA does not contain an ISUP forward dip indicator, processingproceeds to step 490 where a determination is made as to whether aspecial traveling class mark (TCM) is present in the call parameters.This determination is expanded in FIG. 12 as discussed below. If a TCMis present, a CONTINUE return code is returned from the database queryprocessor performing the dip to the relevant switching node and the callis routed on the CdPN.

Referring momentarily to FIG. 12, therein provided is a flow chart thatillustrates the operations to determine if a TCM is present in the call.First, at step 500, a TCM is examined. At step 510 a determination ismade as to whether a special portability related TCM is present (e.g., aTCM of "69"). If no TCM is present, processing proceeds to step 520where a RETURN code is sent back from the database server performing diplogic and processing continues at step 570 in FIG. 13.

If a special TCM is present, a subsequent database query is performed tolook-up and scan for a TCM value used in the relevant network at step530. Thereafter, processing proceeds to step 540 where a determinationis made as to whether the TCM is a MAGIC (i.e., an agreed upon valueamong carriers) value which may or may not be optimized for numberportability. If a MAGIC TCM is not present, a RETURN operation isperformed and processing continues at step 570 in FIG. 13.

If a MAGIC TCM is present in the CNA, processing proceeds to step 560where the CNA is replaced with the NNA as previously determined throughdatabase operations and the call is routed in the communications networkbased on the CdPN (i.e., the NNA).

If no special TCM is present with the CNA, processing proceeds to step570 in FIG. 13 as suggested above for a last determination as to whethera dip has already been performed. At step 570, a determination is madeas to whether the call and the CNA were presented at the currentswitching node that ordered the dip from a new domain network. Thisdetermination is made based on the trunk group identifier (TGID) whichthe call was received at the current switching node that is controllingthe dip process (see FIG. 17 and the discussion thereof for moredetails). This determination allows the present invention to determinewhether a dip has been previously done in the case of where the callparameters normally used for call state tracking as exemplified abovemay have been screened for the call leading to ambiguity regardingwhether the call has already been dipped. If so, to prevent redundantand possibly erroneous processing and routing which may occur as aresult of dipping an NNA instead of dipping a CNA.

If the call was not presented from a new domain network (i.e., from anold domain network which is not capable of database routing local numberportability calls and terminating ported numbers), processing proceedsto step 580 where it is safely assumed that the call was not translatedthereby requiring proper translation to occur (i.e., a CNA<--NNA).

If the call was presented from a new domain network, processing proceedsto step 590 where it is safely assumed that the CNA contains a NNA afterproper translation and the call is properly routed on the NNA in the CNAat step 600.

Referring momentarily to FIGS. 14 and 15, therein provided are flowcharts that expand the operations carried out at step 570 to determine,during the dipping process, whether the call was presented at thecurrent switching node from a new domain network or from an old domainnetwork to effectuate domain partitioning to properly route the call inthe communications network. The databases used to perform the presentinvention's domain partitioning operations (i.e., TRUNK GROUP CLASSMARKING via DBMS operations) are illustrated in detail in FIG. 18.

In particular, at step 610, a determination is made as to whether thecall is a trunk group call on a particular trunk having a particulartrunk group identifier (TGID). If not, processing proceeds to step 620for default call processing (i.e., routing of the call occurs on theCdPN).

If the call is a trunk group call, processing proceeds to step 630 wherea switch administration ID is scanned from a SS7 originating point code(OPC) table (SSPAdmPfx in FIG. 18) of the present switching node or SSP.Thereafter, processing proceeds to step 640, where a determination ismade as to whether an administration record was found. If no record wasfound, processing proceeds to step 620 for appropriate treatment (i.e.,default call processing such as routing the call on the CdPN).

If an administration record was found, a database query is launched inthe SCP to look up or scan for an SSP admin information record and atrunk group ID (TGID) (TRUNKTABLES in FIG. 18).

If, at step 660 in FIG. 15, a TGID was not found during theaforementioned database query, processing proceeds to step 670 where theCNA is assumed to be an old domain number and the call thereforerequires CNA to NNA translation prior to routing.

If a TGID was found, processing proceeds to step 670 where adetermination is made as to whether the trunk is connected to a newdomain network (i.e., has already been dipped). If the trunk group doesnot connect a new domain network based on the trunk group type flag, theCdPN is assumed to be an old domain and the CNA is translated to NNA.

If, at step 670, the trunk connects to a new domain network, processingproceeds to step 680 where it is safely assumed that the call has beenrouted from a new domain network or system and, accordingly, the callhas already been dipped (i.e., properly translated). Thereafter,processing proceeds to step 690 where the call is routed on the NNA aspreviously retrieved.

Accordingly, steps 570-600 of FIG. 13 and steps 610-690 of FIGS. 14 and15 illustrate an important aspect of the present invention. That is,steps 570-600 illustrate the operations that are detailed in thecomputer program listing appendix and which are carried out to bringabout what the inventors have termed "domain partitioning." That is, bydetermining whether a call at a particular switching node (e.g., a LECand/or SSP) was received at such switching node on a trunk group thatwas tied to a new domain network, it can safely be assumed that the callwas translated. On the other hand, if the call was received on a trunkgroup that is tied to an old domain network switching system, then itcan safely be assumed that the call was not previously translated. Assuch, the domains are effectively and appropriately separated orpartitioned to make certain assumptions about the translation status ofa given dialed number or CNA. Additionally, such domain partitioningallows the present invention to realize local area number portabilitywithout performing redundant dips or translations which can bring abouta waste of system resources and erroneous call processing and routing.

Referring now to FIG. 16, therein provided is a flow chart thatillustrates the operations carried out by the presently preferredembodiments of the present invention to bring about portable numberrouting in a communications network as the PSTN. Processing begins atstep 700 where the NNA from the database after the dip was performed isplaced into the CdPN in response message field "xlation".

Thereafter, at step 710, the CNA (which now contains the NNA as a resultof the dip as discussed above) is placed in the generic addressparameter (GAP of SS7/ISUP) (TCM in AIN 0.1).

At step 720, the ANI/II value is set to the MAGIC value and at step 730,the FCI and the nature-of-number are both set to the CdPN.

At step 740, a response message is sent from the database server to theswitching node or SSP for appropriate call routing of the call on theNNA.

Referring now to FIG. 17, therein depicted is a diagram that illustratesthe origination and routing of calls within a communications networkincluding calls from new and old domain switching networks.

In particular, a call may be initiated from an old domain network 760which is connected to switching complex containing an SSP 750 via atrunk group having a trunk group identification number TGID1 770. Thetrunk group identification number TGID1 770 may also be referred to afacility identification number. Old domain network 760 is, itself, notcapable of translating or terminating ported numbers. The SSP, via SS7communication links 810, 820 (e.g., A-Links) communicates over SS7Network 810 to communicate with an SCP 830. SCP 830 has the capabilityto determine if the call was received at SSP 750 from either an olddomain or new domain network via database operations related to TRUNKGROUP TABLE 840.

TRUNK GROUP TABLE 840 contains records that indicate if the trunk groupon which SSP 750 received the call was either a new domain network callor an old domain network call. As such, by determining whether the callwas received from a new domain network or from an old domain network, itis possible to determine if a call had been previously translated andthat a CNA has been mapped to NNA or that such a translation must occur.

Referring now to FIG. 18, therein depicted are database structures thatSCP 830 (FIG. 17) may actually use to determine the trunk group statusof an incoming call to SSP 750 (FIG. 17) to perform domain partitioningto determine if a call requires translation or not.

The usage of the database structures (tables) of FIG. 18 were explainedin regard to the FIGS. 14 and 15.

Although preferred embodiments of the present invention have been shownand described as illustrated herein and in the microfiche appendixhereto, the present invention is not so limited. In fact many changesand modifications may be made to the present invention without departingfrom the spirit of principles of the same which are defined in theappended claims and their equivalents.

What is claimed is:
 1. A method of routing a call based upon a callconnection request including a called number in a communicationsnetwork, comprising the steps of:determining if said called number isequal to a network routing number by examining a call signallingparameter associated with said called number and routing said callwithin said communications network based on said called number when saidcalled number is equal to said network routing number; and identifyingsaid network routing number based upon said called number when saidcalled number is not equal to said network routing number and routingsaid call within said communications network based on the identifiednetwork routing number.
 2. The method of claim 1, wherein saididentifying step is carried out at a first switching node having a firstincoming line having a first incoming line facility identifier andwherein said identifying step identifies said network routing numberbased on said first incoming facility identifier.
 3. The method of claim1, wherein said determining step is carried out at a first switchingnode having a first incoming facility having a first incoming facilityidentifier and wherein said determining step determines if said callednumber is equal to said network routing number based on said firstincoming facility identifier.
 4. The method of claim 1, wherein saidcalled number is a standard ten digit number.
 5. The method of claim 1,wherein said network routing number is a standard ten digit number. 6.The method of claim 1, wherein said called number and said networkrouting number have the same format.
 7. The method of claim 1, furthercomprising the step of determining whether a set of call parametersassociated with said called number includes the call signallingparameter indicating that said called number is a ported number and ifsaid parameter exists, immediately carrying out said identifying stepwithout carrying out said determining if said called number is equal tosaid network routing number.
 8. The method of claim 7, wherein saididentifying step is carried out at a first switching node having a firstincoming facility having a first incoming facility identifier andwherein said identifying step identifies said network routing numberbased on said first incoming facility identifier.
 9. The method of claim1, further comprising the step of determining whether said called numberindicates that a toll call is to be placed and if said toll call is tobe placed, routing said called number through toll call channels withoutperforming said determining and said identifying steps.
 10. The methodof claim 1, wherein said determining step determines if said callednumber is a network routing number based on a facility on which saidcall connection request was received at a capable switching node of saidcommunications network.
 11. A method of routing a call based upon a callconnection request including a called number in a communicationsnetwork, comprising the steps of:determining if said called number isequal to a network routing number and routing said call within saidcommunications network based on said called number when said callednumber is equal to said network routing number; identifying said networkrouting number based upon said called number when said called number isnot equal to said network routing number and routing said call withinsaid communications network based on the identified network routingnumber; and transforming said called number into a customer numberaddress (CNA), wherein said determining step involves determining ifsaid CNA is equal to said network routing number and said identifyingstep is carried out with respect to said CNA.
 12. A method of routingcalls within a communications network interconnecting a plurality ofswitching nodes wherein at least some switching nodes of said pluralityof switching nodes being capable of routing and terminating portednumbers, said method comprising the steps of:generating a callconnection request including a called number; determining if said callednumber matches a trigger indicating that said called number may be aported number and routing said call based on said called number whensaid called number does not match said trigger; determining if thecalled number has been translated into a network routing number when ithas been determined that said called number matches said trigger; andtranslating said called number into a translated network routing numberwhen it has been determined that said called number had not earlier beentranslated and routing the call based on said translated network routingnumber.
 13. A method of routing a call including a called number in acommunications network, comprising the steps of:determining if said callis from a first domain of said communications network as indicated by acall signalling parameter associated with and separate from said callednumber; and translating said called number into a network routing numberresponsive to the determination said call is from said first domain. 14.The method of claim 13, further comprising the step of:routing said callwithin said communications network based on said network routing number.15. The method of claim 13, wherein said called number and said networkrouting number have the same format.
 16. A method of routing a call in acommunication network, comprising;determining whether a call signallingparameter associated with and separate from a called number indicatesthat the number is a network routing number; translating the callednumber into the network routing number responsive to the thedetermination that the called number is not the network routing number;and routing the call using the network routing number.